The OE2DMolDisplay constructor previously threw an
error when initialized with an empty molecule or with a molecule
with no coordinates. A warning is now thrown and the object is marked
invalid (e.g., the OE2DMolDisplay.IsValid method will
return false). In addition, an OE2DMolDisplay object
becomes invalid if the molecule from which it was initialized is modified
(e.g., when atoms/bonds are added or deleted). All OEDepict TK functions
handling an OE2DMolDisplay object now check the
validity of the object prior to use.

Reactions with only product or only reactant components are now
depicted correctly with a reaction arrow and the “+” sign between the
components.